You can use domain.tld but usual practice is hostname.domain.tld where "hostname" can be whatever you want or need, e.g. in case of multiple servers: server1, server2, server3..., or hostname, hosting, primary, etc. If this is new server i would suggest to change now to hostname.domain.tld.

- I often come to the conclusion that my brain has too many tabs open. -Failing at desktop publishing & graphic design since 1994.

Guys, what about nameserver settings in post-installation wizzard? Whatever i type doesn't get resolved from the internet side. Should i use dns management console for my domain and insert A records named "ns1" and "ns2" in it? Or mybe NS records.

And wich dns servers should my virtualmin use? Before installing Virtualmin my primary dns server was set to ISP's dns server and secondary to 8.8.8.8. Will that work for web hosting or the virtualmin installation should use itself as dns server?

I know that will work but is it the recommended way to go? Can we get some admins on this topic please?
I'm by-the-book admin, i try to avoid stuff like editing /etc/hosts file because it's a trick that works when dns servers are not configured properly. In dns resolution process first thing that is checked is the cache on the server, then /etc/hosts file, then the dns server used.

Guys, what about nameserver settings in post-installation wizzard? Whatever i type doesn't get resolved from the internet side. Should i use dns management console for my domain and insert A records named "ns1" and "ns2" in it? Or mybe NS records.
Use ns1.domain.tld in big window and ns2.domain.tld in small and click to not check the servers. One of the reason for this problem is because your domain doesnt have DNS records (probably waiting to be attached to virtual server) and so there is no records for your name servers. This is just one reason why this is happening.

And wich dns servers should my virtualmin use? Before installing Virtualmin my primary dns server was set to ISP's dns server and secondary to 8.8.8.8. Will that work for web hosting or the virtualmin installation should use itself as dns server?
DNS settings are located in resolv.conf and to make it easier to understand here is mine: